Preheat your oven to 300°F (150°C). Line a baking sheet with parchment paper and set it aside.

Carefully separate egg whites and yolks into two clean bowls. Ensure no yolk gets into the whites, as fat will prevent proper whipping.

Add cream of tartar to the egg whites. Using an electric mixer, beat on medium speed until foamy, then increase to high speed until stiff, glossy peaks form. The whites should hold their shape when the beaters are lifted.

In a separate bowl, combine egg yolks, cottage cheese, vanilla extract, sweetener (if using), salt, and cornstarch. Mix until smooth. For extra smoothness, blend briefly using a blender or immersion blender.

Add one-third of the whipped egg whites into the yolk mixture to lighten it. Gently fold using a spatula. Repeat with the remaining egg whites, folding carefully to avoid deflating the mixture.

Gently fold in the blueberries, being careful not to crush them.

Spoon the mixture onto the prepared baking sheet into round mounds or rustic bread shapes, leaving space between each.

Bake for 25–30 minutes, or until the tops are lightly golden and set. Avoid opening the oven during baking.

Remove from the oven and allow to cool on the baking sheet for 5 minutes, then transfer to a cooling rack.